bit movers

[handeli at ocfmail.ocf.llnl.gov]

I need a C function which can move arbitrary
bits around from one memory location to another
with a bit offset of anything. For example,
the call might look like

movebits(a1,ioff1,a2,ioff2,nbits)

where a1 and a2 are char arrays
ioff1 and ioff2 are bit offsets into the
char arrays
nbits is the number of bits to move.
a1 might be source address and a2 might be
destination address.

Anybody have such a function?